BIGACE is an easy-to-use multi-site, multi-language and multi-user Web CMS, written in PHP/MySQL. Uses FCKeditor for HTML editing. Features: Content versioning, workflows, user and right management. Many Smarty Templates and extensions available.
- Multiple websites in one instance
- Multiple languages, users, groups
- 5-minute installer
- Easy to use
- Plugins available
Mutli-site support is the best I've seen.